Like this?

(B)lue on port, initially is required to keep clear of (Y)ellow on starboard (RRS 10)

Y, overlapped outside when the first of them reaches the zone is required to give B mark-room (RRS 18.2(b)), and if B while sailing within the mark-room to which she is entitled does not keep clear of Y, B is exonerated by RRS 43.1(b). 

@4, Y has gybed onto port, to windward of B and is required to keep clear of B (RRS 11), and continue to give B mark-room.

@5, B changes course to windward, giving Y room to keep clear, and Y keeps clear.

B did not become overlapped to leeward of Y from clear astern, so B has no proper course limitation under RRS 17 .

No rule broken.

Subject to RRS 16 boat A can luff up to head to wind and boat B is required to keep clear, RRS 11.

Somewhere between positions 4 and 5 it would seem to me that the blue boats fastest course to finish is to gybe . To not do so is not her “proper course”. So does rule 18.4 apply? Ie. “when an inside overlapped ROW boat (blue at 4) must gybe at a mark to sail her proper course, until she gybes she shall sail no further from the mark than needed so sail that course”

Stephen Broadbent

Said Created: Today 09:41

Good consideration.

The test for RRS 18.4 is ... must gybe at a mark to sail her proper course ....

B is at the mark @4.  At that point, to finish as soon as possible she need only bear away slightly, not gybe.

So the test is not met and RRS 18.4 does not apply.

Even if position @5 was relevant, within 1 boat length of the finishing line, I still think her proper course would just be to bear away , not to gybe.

John
I get your point
My counter is, I would gybe because I think it’s faster and is therefore the proper course.
Your argument is that the proper course is simply to bear way and because that does not involve a gybe therefore 18.4 does not apply. This gives the added benefit that you can luff and not bother to actually bear way and finish. Just does not seam fair to me.
I think there comes a point when blue is luffing to become parallel with the finish line, then it becomes indisputable that her proper course is to gybe and she must do so under 18.4
There must be cases about room to round in a seaman like manner etc that I have not looked up

Thanks. The consensus appears to be that blue is fine. I was the blue boat in the race and I started over-thinking the situation later that day when I remembered that a boat being given room at a mark can only maneuver so as to sail her proper course. But I didn’t need room since my course already had me making the mark, the other boat had to gybe in order to get to the line, she had to gybe (or duck me) in order to not take away the room I was entitled to, and I became the leeward boat during the sequence. I was primarily concerned with whether heading up (left) would be considered not sailing proper course while being given room since there was overlap when I entered the zone. 

Thanks. The consensus appears to be that blue is fine. I was the blue boat in the race and I started over-thinking the situation later that day when I remembered that a boat being given room at a mark can only maneuver so as to sail her proper course. But I didn’t need room since my course already had me making the mark, the other boat had to gybe in order to get to the line, she had to gybe (or duck me) in order to not take away the room I was entitled to, and I became the leeward boat during the sequence. I was primarily concerned with whether heading up (left) would be considered not sailing proper course while being given room since there was overlap when I entered the zone. 

And to the discussion about whether I should gybe, the wind angles would not have required a gybe by me (blue) at any point of the sequence to make the line. I could either just keep going to the line and possible get passed doing so because yellow came in with more speed or use my leeward advantage to keep him away from the line until I was close enough to bear away from him and “shoot” the line, still on port. 

Stephen, the term “proper course” is applied differently in the various rules in which it is used. 

When a protest occurs based upon 2 boats’ differing opinion of what one boat’s proper course is at the time, it often comes down to what is reasonable (we don’t have the counter-factuals to test every possible course to see which one was the fastest). 

Also, remember that when “proper course” is analyzed, the other boat referenced in the rule is removed (def: proper course says “.. in the absence of the other boat..”). In 18.4, the “other boat” is the outside boat, as 18.4 limits where the “inside” boat can sail. 

OK … now scroll up to John’s drawing .. and remove Yellow (the outside boat) … only Blue remains on the drawing.  As Yellow protesting Blue are you going to say that if you were Blue all alone … you would have gybed at the pin to finish?… with all that line ahead of you all by yourself?  

Or would you have sailed on port gybe and turned into the line at the last moment (or simply continued with speed on your point of sail)?

Stephen, it might be “proper course” but he is not at the mark. He is below the mark and as soon as any part of his hill crosses the finish line there is no proper course. 

When an inside overlapped right-of-way boat must gybe at a markto sail her proper course, until she gybes she shall sail no farther from the mark than needed to sail that course. Rule 18.4 does not apply at a gate mark.

So she does not need to gybe to sail her proper course at the mark.   B is the leeward boat, and therefore has the right of way and no longer needs to stay in the mark room lane nor constricted to sailing to the mark.   I do not think any rule was broken. 

 In common usage,  a gate can be said to be "a space between two markers through which a competitor must pass". I would therefore consider the marks of the start/finish line to be gate marks and rule 18.4 does not apply at these marks.

In this instance Blue doesn't have "a" proper course, she has a variety of course choices that she may plausibly consider proper. One choice might be to bear away to the line, another might be to gybe to the finish. Yellow doesn't really have any say in which proper course Blue chooses.

Once the boats leave the pin zone, 18 is off and Blue has no obligation to sail a proper course or below her proper course (no 17). I would submit that if, for tactical reasons, Blue then chose to continue to luff Yellow away from the finish so other boats could finish ahead of Yellow and improve Blue's regatta score, that would be permissible (see case 78).

If they get into the zone of the committee boat, Yellow would then be inside and Blue would owe Yellow mark-room. At that point Yellow could bear away or gybe to finish.

Murray … here is a Q&A on gates vs finish-lines 

https://www.racingrulesofsailing.org/cases/2359

Stephen, Paul, Tim,

Proper course.

Listen to the OP evidence

Stephen Broadbent

said Created: Yesterday 10:42

USA Appeal US20

 

Definitions, Mark-RoomRule 11, On the Same Tack, OverlappedRule 14, Avoiding ContactRule 18.2(b), Mark-Room: Giving Mark-Room

International 110 664 vs. International 110 64
Mark-room is not defined to allow an inside boat without right of way to sail to a mark in a tactically desirable manner.

Conversely, a boat entitled to mark-room that also has right of way is not constrained to a seamanlike rounding.

John A. Thanks. And your last comment made consider that this is not really a “mark rounding”. I merely had to poke my nose across some part of the finish line. I just wasn’t sure if entering the zone with overlap tied me to the room rule even though I didn’t really require it based on the fact that I was in no danger of not being able to make the line. And I wasn’t sure if still being in the zone after having room rights due to the overlap negated my option of using my leeward advantage once the other boat gybed. Appreciate the input. 

And just to wrap this up. If this had been a windward finish, the situation would have been completely different, right? 18.1(a) 

Eric,

The finishing mark was not a rounding mark, but it was a mark at which rule 18 applied.

You needed mark room to relieve you of the requirement to keep clear of Y, approaching you on starboard tack.

Yes, it would have been different finishing on a beat to windward. 

Eventually Yellow acquires mark room at the RC end...

John Allen's analysis seems fairly much correct assuming Y was the outside boat when one of the two entered the zone. It appears that B entered the zone first, if I understand the facts correctly so this would logically seem to make Y the outside boat.  However, if B does not sail to the mark in a seamanlike manner then she has abused the "corridor" to which she was entitled by mark room and once given the corridor, Rule 18.2(d) says Rule 18.2(b) and (c) cease to apply.  If B doesn't sail straight to the mark it would need to keep clear of Y who could sail right to the mark, gybe there in front of B as the right of way boat and since B had to keep clear as the keep clear boat on port it would have a hard time arguing that Y gybed to close too give her a chance to keep clear, I would think.  In other words I don't think B can sail past the mark.  

However, if Y was first into the zone who would be the "outside" boat?  Y would be closer to the mark, so would seem to be the "inside" boat, although it would be unable to fetch the mark without gybing.  If Y were the inside boat, then B must give it mark room as they are overlapped and allow Y to get to the mark in a seamanlike manner, whether Y had to gybe or not. B would not be able to luff up Y after it gybes because the state of affairs is determined at the entry into the zone and does not change thereafter.  (18.2(c)(2) would require Y to not sail above its proper course if B were to become overlapped to the inside after in the zone, but that doesn't seem relevant to Eric's question.)